[Dalvir]

Last month I took the car to a main vauxhall dealer and gave them the following sheet with dates when certain tasks were performed:-

Problem with this car: When started from cold in the mornings, it hesitates acceleration for the first 2 minutes. Hesitation spots are also noticeable at times even when the car has warmed up. There are no fault codes given out by the ECU.

The following maintenance work has already been carried out on this vehicle:-
Engine oil & oil filter – 13/2/2011
Pollen filter element – 25/2/10
Hydraulic fluid top up – March 2011
Air cleaner element - May 2009
4 Bosch Spark plugs – 16/2/2011
Timing belt, tensioner roller & water pump - Sept 2008
Fuel filter - May 2009
Air mass sensor - Dec 2009
Ignition module & all 4 leads changed– March 2010
Idle stepper motor changed (but software not updated) – 25/3/2010
EGR valve changed– June 2010
Water temperature sensor – May 2010
Air temperature sensor –Aug 2010
New catalytic converter - 25/2/2011
Battery – 24/3/10
Complete coolant drain and antifreeze change – 11/2/11
Breather box located at front of top cam cover cleaned with gunk - April 2011
Purge valve hoses checked for blockages. EGR valve removed & contamination removed by sucking air with a vacuum cleaner from ports underneath it - March 2011
Throttle body/idle stepper motor cleaned thoroughly & all connecting hoses checked for blockages and cracks – March 2011

What has shown to help: Cleaning of spark plugs. Cleaning of throttle body. EGR valve ports contamination removal. Cleaning of breather box. Performing these tasks has shown to eliminate or reduce the problem for a month or two but it will then come back.

What next: Engine management systems check is required to find out if there is something that has been missed out.

After performing the technical tests, they could not find anything wrong to which they could pinpoint the problem to. The have said that there are no fault codes in the system and to wait for the fault to progress and then get it retested.

In attempt to clear the fault on my car, I fitted a new quality Lambda sensor yesterday. I am afraid it made no difference to the problem. The car has a low mileage of under 68,000 miles.

If the car is used with gentle acceleration, it is normally fine. However if sudden acceleration is applied, it is likely to jerk. On steady routes it gives an impressive mileage of 40 miles/gallon reading on the car’s own recording meter even with this fault. The car’s average annual mileage is 4 to 5 thousand miles per annum. The only way forward is to continue changing parts and hope for the best.

The next item is the the cam sensor. I have been advised to check it’s wiring for breaks and the plastic covering could also get chipped off due to age hardening. There is a modified kit available for X20XEV model. However I must point out that the car can rev over 4500 and hence raises a serious concern if it is the problem.

The other area is the fuel injectors. The only care I have done to them is the use of Redex to keep them clean. Should all fuel injectors be changed?

I look forward to any comments on the above issue as to what I should check or change first and I am confident that with the kind help of other members, I will be able to clear this fault.

[ASTOBBS]

get them to check the fuel rail pressure.

Also there is often a vacuum tube coming from the top of the fuel pressure regulator, from memory I don't think its supposed to be used on the X20XEV. Have a look to see
1. if it is connected anywhere
2. and if so where ie. before or after the butterfly plate
3. if its connected at all, try disconnecting it, as an experiment, but blank off to prevent an air leak into the engine.

If you had a CMP (camshaft position) sensor fault it would show up as a fault code.

Does the hesitaion happen at a certain throttle position? check signal voltage from TPS for a jump/step.

you've covered alot but theres alot more to check still.

[Dalvir]

The followings were done since my last update:-
It was noticed that since changing the Lambda/oxygen sensor, the dle speed became stable.
EGR valve blanking tried but no difference & hence unblanked. Fuel filter changed.
Fuel injectors sent away & ultrasonically cleaned. This resulted in reclaim of 64cc/min. Engine has more power now & the cold running problem solved.
Throttle body removed and cleaned thoroughly & all connecting hoses thoroughly checked for blockages and cracks. Most of the electrical connectors have been sprayed with electrical contact cleaner.

Cam sensor with modified wiring loom (Siemens) fitted. Crankshaft sensor and Fuel pressure regulator changed (genuine Vauxhall). But there was no change in hesitation problem noticed.

Car was then taken to the Vauxhall dealer again and instructed to check fuel pressure, TBS and timing. He found that the throttle cable was incorrectly set. It needed resetting. At last the car is fine now. It runs without any form of hesitation and full of power.

[ASTOBBS]

glad you got it sorted, but thats a long list of replacement parts to get down to a throttle cable issue.
Atleast you've got a virtually brandnew engine - electrically speaking.